Detection of changed lines fails if project base directory is not the root of the git repository

Details

Description

To reproduce, create for example a git repository containing:

project/
project/sonar-scanner.properties
project/src/file.js

Scan the project inside project. Introduce and commit, in a different branch, some changes in file.js and analyze it specifying sonar.branch.name and sonar.branch.target.
The Git SCM plugin will be able to detect that there is 1 changed file, but no changed lines are reported.
If the git repository's root is inside `project`, it works.